It's a moment that not all parents have experienced, but that many of us fear: You're enjoying a passionate encounter with your partner, oblivious to the pitter-patter of little feet until it's too late.
Have you just scarred your kid for life? Certainly not -- but, depending on your child's age, you might have some explaining to do.
"Being walked in on during sex is a very common experience -- and a great example of why it is important to knock first, and always respect someone's privacy," says sexologist Logan Levkoff.
"But before you say anything to your child, you are going to need to determine what they heard, saw, and if they even care about what was going on."
I believe that how you should address these questions or concerns depends on your child's age.
For example, most experts agree that parents shouldn't worry about being intimate near their baby.
"Many families choose co-sleeping with babies, or having babies in the parental bedroom," explains psychotherapist Jennifer Naparstek Klein.
"It doesn't seem harmful for there to be parental sexuality while a baby snoozes or is nearby in various states of alertness. Babies cannot process what the parents are doing, so it has no significance to them."
Here are some considerations for every age group:
Toddlers: Some young children may be oblivious to sex, while others may need reassurance.
"Children sometimes think something violent or frightening is happening, and that should be addressed," says sex therapist Margie Nichols. "When my son was a toddler, he thought his stepdad was 'hurting' me because, well, we were way too loud and even very late at night my son could hear us."
Explain that you and your partner were having a private moment and that you weren't hurting each other, and leave it at that unless your child has more questions.
Elementary-age children: Kids this age have some curiosity about sex, but at the same time, they generally want to steer away from the subject.
"Always follow your child's lead on what they can handle," suggests Klein. "If they get too uncomfortable with sex talk, save it for a later time."
Tweens: By this age, many kids know what's going on and may even make noises of loud disgust if they walk in on you by accident. Yet it's a great time to give your child the idea that sex is a private, enjoyable activity that takes place in adult relationships, says Nichols.
Teens: "Older kids are sometimes amused when they guess that their parents have been sexual, but if it's in their faces too much of the time, it can create discomfort and anxiety," says Klein.
"Teens can better handle the idea of their parents as sexual beings, but they really don't need to see it. Ask any teenager: They'll tell you themselves whether they want to see their parents getting it on. I promise you, the answer is no."
But these days, you don't just have to worry about your child walking in on a private moment -- you may also have to explain other things encountered in or out of the home, such as sex toys, self-pleasuring and even pornography.
"The average age a kid sees porn is 10. It's everywhere and it's naive to think your kid won't see it," says sexual health educator Amy Lang of Birds + Bees + Kids.
"Tell them about porn before they stumble across it: 'Sometimes people look at pictures or videos of people having sex. This is called pornography, or porn. It's not for kids, and your heart and mind aren't ready to see something like this. You won't be in trouble if you do, but I need to make sure you are OK.'"
However you choose to talk about sex, "you want to remain low-key, not emotional. Try to assess where your child is coming from and what his or her unspoken questions might be, give appropriate information and be sex-positive," says Nichols.
Take some steps to prevent a repeat performance: Install a lock on your bedroom door, encourage kids to knock, play soft music or the TV for white noise at night, and schedule "private parent time" when your child knows not to disturb you.
But don't keep all intimacy behind closed doors. "Being affectionate -- not sexual -- in front of your children can be a wonderful thing," says Levkoff.
"Kids should know that there is physical love and intimacy and we model for them how to express that in healthy ways." So kiss, hug, cuddle, and hold hands with your partner.